1. Field of the Invention
The present invention relates to display systems for aircraft, and more particularly to the aircraft's primary flight display.
2. Description of the Related Art
The flight deck of an aircraft has several displays that present information about the aircraft operation and flight conditions. These displays are employed to monitor various events in real-time and to provide a visual indication of such events in graphical form thereby allowing an observer to make decisions based on the occurrence of one or more specific events in particular relationship to each other. One of the key instruments used by aircraft pilots is a display commonly referred to as a Primary Flight Display, or PFD, used to operate and/or maneuver aircrafts during take-off; flight and landing. When the aircraft is in flight, the PFD provides numerous information about the aircraft, such as its heading, roll (the angle of wings relative to horizontal), and pitch (the degree to which the aircraft nose is pointing up or down relative to the horizontal. The graphics depicted by the PFD are arranged in a standard format to allow a pilot to quickly locate particular information by focusing in on the specific part of the display screen to which the information has been assigned.
FIG. 1 depicts a standard graphic and textual information arrangement on a PFD. Note that textual information is included with other graphical information to allow the pilot of the aircraft to determine the status of various sensor readings being provided to the aircraft while in flight. The sensor readings present information from different sources which are converted to graphical signals for display on the PFD.
The depiction of the Primary Flight Display in the drawings has been annotated to identify the types of displayed information used by the pilot while the aircraft is in flight, taking off or landing. The “inverted V” shown at generally the center of the display represents the aircraft in reference to the horizontal. The “Zero Roll Reference” is a reference point for determining how much “roll” the aircraft is experiencing during flight with a “Roll Bug” depicting the degree that the aircraft is deviating from a zero roll orientation. The roll is a measure of how much the aircraft is rotated about its longitudinal axis (i.e., the axis that is oriented lengthwise of the aircraft). Also, various speeds of the aircraft are displayed. Specifically a speed tape on the left edge of the PFD indicates the forward speed of the aircraft and an arcuate scale in the lower right corner provides a vertical speed indication. An altitude indicator displays the present altitude in relation to a desired altitude for the aircraft. A heading tape along the bottom edge of the PFD presents information regarding heading of the aircraft and it deviation from a desired heading.
A pitch ladder designates the pitch of the aircraft in degrees with respect to horizontal. The standard PFD has the region below the horizontal uniformly colored brown to correspond to earth and the region above the horizontal uniformly colored blue to correspond to the sky. Pitch is rotation around a transverse axis of the aircraft parallel to the wings. The pitch ladder has a linear scale with five degree increments up and down indicated by equally spaced L-shaped markers with the markers for 10 and 20 degrees being labeled with those numerals. The pitch ladder moves vertically on the display with the current pitch of the aircraft being indicated by alignment of a point of the ladder with the apex of the stationary inverted V-shaped aircraft symbol. In the exemplary indication on the PFD in FIG. 1, the aircraft is level at zero pitch, however if the nose of the aircraft tilts up the horizontal line at zero pitch drops below the aircraft symbol and the pitch ladder also moves downward on the PFD until the degree indication corresponding to the actual pitch is laterally aligned with the apex of the aircraft symbol.
Various other information can be provided by the PFD.